This invention relates generally to the connection of flexible polymeric tubing sections, and more particularly to methods and apparatus for connecting such tubing sections so as to maintain a sterile condition in an interior passage of the tubing.
Medical containers with tubing are used for various medical procedures such as kidney dialysis, intravenous delivery of therapeutic fluids, delivery of nutritional fluids; delivery of blood, blood components, and blood substitutes. Fluid containers and tubing are also widely used in other industries such as the food industry and the chemical industries.
One example in the medical context is when two flowable medical products (e.g., liquids and mixtures of liquids and solids) need to be delivered to the patient at the same time, but the two products cannot be sterilized in the same way.
It is possible to manufacture both products (even as a mixture) in an aseptic environment. This is expensive and may not lead to a level of sterilization in the final product which is superior to making and packaging the products in a nonsterile environment and subsequently sterilizing both the products and the package. Another option is to package the products separately and connect them at the time of use. However, this requires a sterile connection of the packages, and more specifically a sterile connection of tubes connected to the packages.
As another example requiring sterile connection of tubing, flexible medical tubing is used in systems for treating renal disease. The balance of water, minerals and the excretion of daily metabolic load is no longer possible in renal failure. During renal failure, toxic end products of nitrogen metabolism (urea, creatinine, uric acid and others) can accumulate in blood and tissues. This condition is commonly treated with dialysis.
Dialysis removes waste toxins and excess water from the body that would otherwise have been removed by normal functioning kidneys. Dialysis treatment for replacement of kidney functions is critical to many people because the treatment is lifesaving. One who has failed kidneys could not continue to live without replacing at least the filtration functions of the kidneys. Hemodialysis and peritoneal dialysis are two types of dialysis therapies commonly used to treat loss of kidney function.
In general, hemodialysis treatment removes waste, toxins, and excess water from the patient's blood. The patient is connected to a hemodialysis machine and the patient's blood is pumped through the machine. Catheters are inserted into the patient's veins and arteries to connect the blood flow to and from the hemodialysis machine. As blood passes through a dialyzer in the hemodialysis machine, waste, toxins, and excess water are removed from the patient's blood and the blood is infused back into the patient. Many tubes are used in the process that must be connected or disconnected. Peritoneal dialysis typically utilizes a dialysis solution, or dialysate, which is infused into a patient's peritoneal cavity. Waste, toxins and excess water pass from the patient's bloodstream through his/her peritoneal membrane and into the dialysate. The transfer of waste, toxins and water from the bloodstream into the dialysate occurs due to diffusion and osmosis, i.e., there is an osmotic gradient across the membrane. The spent dialysate is drained from the patient's peritoneal cavity to remove the waste, toxins and water from the patient. After the spent dialysis is drained, it is replaced with a fresh dialysate solution.
In peritoneal dialysis, a patient has a catheter implanted in his/her peritoneal cavity with an end protruding from the patient. The protruding end of the catheter terminates with a section of tubing known as a transfer set. The transfer set is typically made from a silicone material and must be periodically replaced. The transfer set is provided to connect the patient to dialysate fluid bags or discharge bags. The transfer set typically has a spike that connects to an access port positioned in a tube associated with the drain bag or dialysate solution bag (dialysate set). In general, the patient manually stabs the port with the spike to connect the transfer set to the dialysate set. The patient connects the tube in the transfer set to a drain to allow spent dialysate fluid to drain from the peritoneal cavity. Next, the patient is connected to a bag of fresh dialysate and manually infuses the fresh dialysate through the catheter and into the patient's peritoneal cavity. When the patient completes treatment, the port is pulled off the spike and a cap is placed on a spike until the patient is ready for the next treatment. When the patient disconnects the catheter from the fresh dialysate bag, the dialysate dwells within the peritoneal cavity to draw waste, toxins and excess water from the patient's bloodstream to the dialysate solution. After the dwell period, the patient repeats the manual dialysis procedure and drains the spent dialysate from the peritoneal cavity.
Accordingly, during dialysis treatments such as those described above, the patient is required to connect and disconnect the catheter and transfer set from the fill or drain line (or tube) a number of times. Some devices are available today to assist the patient during the process when using specialized sterilization equipment. However, by and large, these connections and disconnections are performed manually.
One such device incorporates a heated wafer or hot knife that physically contacts the tubing to cut it by melting the tube and joining two tubes together or melt-sealing the tube ends. Typically, heated wafer applications involve a “melt and wipe” process. In peritoneal dialysis, for example, a patient must drain spent dialysate or replenish his/her peritoneal cavity with fresh dialysate. To this end, the patient must connect the transfer set tubing to a tube extending from either a drain bag or a bag containing fresh dialysate. In one “melt and wipe” process, the transfer set tubing is bent in a U or V-shape to fit into a first U or V-shaped tube holder. Similarly, the bag-side tube is bent in a U or V-shape to fit into a second U or V-shaped tube holder adjacent the first tube holder. A heated wafer moves across the space between the two tube holders and physically contacts the tubing at the bend junction of the U-shape or V-shape. As the heated wafer contacts the tubing, it melts the tube at the bend junction of the U-shape or V-shape. The wafer then wipes the melted tubing material and removes the material from the area between the first and second tube holders. The two holders are brought together and two connections are made. In the first connection, the transfer set tubing is connected to the bag-side tube and the dialysis process is ready to begin. In the second connection, the wasted tube material from the transfer set tubing and the bag-side tube is connected together and discarded.
In order to disconnect the patient from the bag, hot knives are used to cut the tube. An example of a known disconnecting process with the hot knives involves two tubes that are placed side by side across two tube holders. One of the tubes is a short tube having two sealed ends. Generally, the tube holders include a ridge at one end of the tube holder to flatten a portion of the tube to stop fluid flow. The hot knife severs each tube into two pieces. After the hot knife cuts the tube, one of the tube holders moves in relation to the other tube holder. The tubing is “swapped,” realigned with one of the cut portions of the short tube, and connected to it—thus, a disconnection is made between the patient and the bag.
These devices have a relatively low level of reliability due to the inconsistency in melting and cutting processes. The inconsistency of operation can result in imperfect seals, leading to leaks, and bacterial infiltration which may lead to infection or peritonitis. Moreover, both connections require the heated ends of the tube to be uncovered and exposed to the surrounding environment before the connection is made. This can lead to contamination of the tube ends, and ultimately of the interior of the tubes, even if the device works perfectly.
The interior passages of the tubing sections are initially sterile, but cutting the tubing sections so that connections of adjacent sections can be made exposes the interior passages of the tubing sections to the surrounding environment, allowing them to potentially become contaminated with airborne contaminants, e.g., bacteria. Moreover, if the tubing sections are open, solid material from the unsterile exteriors of the tubing sections could enter the tubing sections. In the applications just described, it is impractical to engage in a resterilization procedure every time a new connection of tubing sections is made. Accordingly, it is recognized that the interior passages of the tubing sections need to be isolated while the tubing sections are being connected together.
In order to avoid exposure of the interior passage of each tubing section, it is known to clamp the end portion of the tubing section shut before an end portion of the tubing section is cut. However, axially facing surfaces at the very ends of the tubes are exposed to their surroundings. In some systems a hot blade or other heated surface is brought into contact with the exposed ends of the tubing sections to bring them up to melting temperature. The ends of the two tubing sections are then brought together so that the melted ends fuse, connecting the tubing sections together. The clamps collapsing the respective end portions of the tubing sections are released and the tubing sections open, defining a continuous, sealed interior passage through the connected tubing sections. In time, however, the heated blade or other surface becomes fouled with the plastic material of the tube, requiring cleaning to maintain operability. Moreover, it is necessary to apply enough energy in heating the ends so that they do not drop below a temperature at which fusion will occur before the two ends of the tubing sections are brought together.
Other tube connection systems have applied heat to the ends of the tubing sections without requiring direct contact of heating elements with the tubing sections. Examples of these types of systems are disclosed in the following patent applications, the disclosures of which are incorporated herein by reference: Apparatus and Method for Connecting and Disconnecting Flexible Tubing, U.S. application Ser. No. 10/061,835, filed Jan. 31, 2002; Coupler Member for Joining Dissimilar Materials, U.S. application Ser. No. 10/251,681, filed Sep. 20, 2002; Laser Weldable Flexible Medical Tubings, Films and Assemblies Thereof, U.S. application Ser. No. 10/251,682, filed Sep. 20, 2002; and Laser Weldable Flexible Medical Tubings, Films and Assemblies Thereof, U.S. application Ser. No. 10/251,683, filed Sep. 20, 2002. These systems may employ a laser for heating. One drawback of these systems is that a substantial amount of power is required heat the end portions of the tubing sections. The conventional medical tubing material does not absorb the energy of the electromagnetic radiation well, so considerable energy is required to melt the tubing. Moreover, these methods have still required heating, followed by movement of the tubing sections into engagement. The axially facing surfaces of the end sections are exposed for some considerable time to the surroundings. Moreover, the axially facing surfaces still have to be heated enough so that they do not cool down too much before they are moved into contact with each other.